P0273 OBD-II Trouble Code: Cylinder 5 Injector Circuit Low

P0273 code definition

This code is defined as cylinder 5 injector circuit being low.

What the P0273 code means

The P0273 trouble code means that the PCM (powertrain control module) has found a voltage level in the fuel injector from the cylinder #5 is lower than is acceptable. Basically, the fuel injector is malfunctioning.

When this happens, it can set off a ripple effect that goes through the rest of the engine.
This is why the engine’s operational parameters will actually change when this code is logged. For example, to combat the lean mixture occurring because of a fuel injector unable to provide a sufficient spray pattern, the fuel mixture to all the other cylinders becomes richer. As a result, fuel economy suffers.

At the same time, a lean fuel mixture is going to make the cylinder work harder which, in turn, will increase the temperature of its head. The result is detonation. To stop this from happening, the PCM will retard the timing which will produce a lack of power in the engine.

What causes the P0273 code?

There are a few reasons that could result in the P0273 code. These are:

The #5 fuel injector is most likely faulty; it could be damaged or simply dirty.

The connector or wiring associated with the #5 fuel injector could be damaged.

An internal return spring could be weak or damaged and hurting the #5 fuel injector’s performance.

If none of these issues are found to be responsible, the problem could be that the PCM isn’t working correctly, but this is very unlikely.

What are the symptoms of the P0273 code?

This trouble code could come with a large number of symptoms. The Check Engine Light will definitely turn on. As we mentioned above, its impact can be widespread and end up affecting other components in the vehicle.

Whenever a fuel injector isn’t working correctly, the vehicle is going to start needing more gas to continue performing. The #5 cylinder could also crack because of having to work so hard.

Even with the PCM’s best efforts, the engine may have a tough time starting. It will most likely struggle to accelerate on the road or even stall. It might misfire as well.

How does a mechanic diagnose the P0273 code?

To diagnose the problem behind this code, the mechanic will:

Start by using an OBD-II sensor to see which trouble codes have been stored

Inspect the #5 fuel injector

Examine the wiring leading to the #5 fuel injector

Check the power supply

Common mistakes when diagnosing the P0273 code

Although this type of code is almost always stored because of a faulty fuel injector, that’s no reason for a mechanic to rush to judgment and immediately replace it. A comprehensive diagnostic process must be applied to test every possibility.

Furthermore, most mechanics will know the fuel injector is involved just by listening to the owner describe the symptoms listed above. Again, though, they must take their time with assessing the situation. If they don’t do a scan, they may fix the fuel injector and clear that code but not realize that other problems exist.

How serious is the P0273 code?

This problem should be treated very seriously. It’s not going to put anyone’s life in danger, but it has the possibility of completely ruining an engine if left untreated for too long.

Fortunately, it will most likely become impossible to ignore before this happens, but it can still do lots of expensive damage before then.

Additional comments for consideration regarding the P0273 code

Need help with a P0273 code?

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